Magnetic order and ballistic spin transport in a sine-Gordon spin chain

Huddart, B. M.; Gomilšek, M.; Hicken, T. J.; Pratt, F. L.; Blundell, Stephen J.; Goddard, Paul; Kaech, Sydney; Manson, Jamie L.; Lancaster, Tom

doi:10.1103/physrevb.103.l060405

Cited by 7 publications

(4 citation statements)

References 45 publications

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“…This corresponds to the exchange anisotropy of YZGO. With XY anisotropy, the transport has been suggested to switch over to ballistic character [25], and examples of ballistic spin dynamics have also been identified in μSR studies of spin chain systems [26,27].…”

mentioning

confidence: 99%

Spin dynamics, entanglement, and the nature of the spin liquid state in YbZnGaO4

Pratt

Lang²,

Steinhardt³

et al. 2022

Phys. Rev. B

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Electron spin dynamics was studied down to 80 mK in the triangular-lattice quantum spin-liquid candidate YbZnGaO 4 using muon spin relaxation, finding no evidence for freezing or ordering of the Yb spins. The muon spin relaxation rate can be represented by the sum of two contributions, one dependent on longitudinal magnetic field and the other independent of field. The field-dependent term follows the form expected for two-dimensional diffusion of mobile spin excitations. The spin-diffusion rate obtained for these excitations in the high temperature paramagnetic regime is comparable with the exchange coupling frequency J/h, reducing significantly in the low temperature quantum regime. This slowdown is assigned to the effect of quantum entanglement. The exchange coupling J is estimated to be 2.0(2) K from the crossover between the two regimes. The field-independent term is only weakly dependent on temperature, and at 15 K its absolute value is consistent with dipolar coupling of the muon to the three Yb moments closest to the muon site, where the spin dynamics of these moments is determined by exchange fluctuations. The temperature-dependent properties in the quantum regime are compared against the three possible U(1) spin-liquid models that have been obtained for the strongly spin-orbit coupled triangular lattice by Y.-D. Li, Y.-M. Lu, and G. Chen [Phys. Rev. B 96, 054445 (2017)]. The comparison with theory takes published specific heat and thermal conductivity data into account, along with the spin-diffusion rate obtained from the muons. It is found that the nodal spin-liquid model U1A11 containing both linear and quadratic nodes provides better agreement with experiment than either the U1A00 spinon Fermi surface (FS) model or the U1A01 model that contains only linear nodes.

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mentioning

confidence: 99%

Spin dynamics, entanglement, and the nature of the spin liquid state in YbZnGaO4

Pratt

Lang²,

Steinhardt³

et al. 2022

Phys. Rev. B

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“…This assignment gives an estimate µ Cu ≈ 0.38µ B for the ordered moment. 76 There have been claims, 77 supported by some experimental evidence, 78 that a muon implanted in some spin chains could form an unusual spin-singlet state, not unlike that found in the Kondo effect. However, results on materials such as Cu-PM and the linear chain Cu(pyz)(NO 3 ) 2 , 79 do not provide evidence for the realization of these states.…”

Section: Molecular Systemsmentioning

confidence: 95%

“…The staggered molecular spin chain [pym-Cu(NO 3 ) 2 (H 2 O) 2 ] (pym = pyrimidine), known as Cu-PM is a good example. 76 Here magnetic order was detected using muons at T = 0.23 K. Three distinct classes of muon stopping site were determined [Fig. 7].…”

Section: Molecular Systemsmentioning

confidence: 99%

DFT + μ: Density functional theory for muon site determination

Blundell

Lancaster

2023

Applied Physics Reviews

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The technique of muon spin rotation (μSR) has emerged in the last few decades as one of the most powerful methods of obtaining local magnetic information. To make the technique fully quantitative, it is necessary to have an accurate estimate of where inside the crystal structure the muon implants. This can be provided by density functional theory calculations using an approach that is termed as DFT + μ, density functional theory with the implanted muon included. This article reviews this approach, describes some recent successes in particular μSR experiments, and suggests some avenues for future exploration.

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“…Theoretical work has focused mainly on 1D systems and the XXZ model, where diffusive spin transport is expected for exchange anisotropy on the Ising side of the Heisenberg point [5,6]. With XY anisotropy, the transport has been suggested to switch over to ballistic character [5,6] and examples of ballistic spin dynamics have also been identified in µSR studies of spin chain systems [11,12]. The relaxation measured in a LF-µSR experiment can be expressed as being proportional to the spectral density of the spin fluctuations J(ω) with the probe frequency ω being proportional to the applied field [13].…”

Section: Introductionmentioning

confidence: 99%

Studying spin diffusion and quantum entanglement with LF-µSR

Pratt

Lang

Blundell

et al. 2023

J. Phys.: Conf. Ser.

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LF-µSR studies have previously been used to study the diffusive 1D motion of solitons and polarons in conducting polymers. This type of study was also applied to investigating the diffusive motion of spinons in spin-1/2 antiferromagnetic chains. Recently the method has been extended to examples of 2D layered triangular spin lattices which can support quantum spin liquid states, such as 1T-TaS2 and YbZnGaO4. These systems are found to show spin dynamics that matches well to 2D spin diffusion, such a model being found to provide a much better fit to the data than previously proposed models for spin correlations in such systems. In YbZnGaO4 the diffusion rate shows a clear crossover between classical and quantum regimes as T falls below the exchange coupling J. That the spin diffusion approach works well in the high T classical region might be expected, but it is found that it also works equally well in the low T quantum region where quantum entanglement controls the spin dynamics. Measurement of the diffusion rate allows a T dependent length scale to be derived from the data that can be assigned to a quantum entanglement length ξ E. Another entanglement measure, the Quantum Fisher Information F Q can also be obtained from the data and its T dependence is compared to that of ξ E.

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Magnetic order and ballistic spin transport in a sine-Gordon spin chain

Cited by 7 publications

References 45 publications

Spin dynamics, entanglement, and the nature of the spin liquid state in YbZnGaO4

Spin dynamics, entanglement, and the nature of the spin liquid state in YbZnGaO4

DFT + μ: Density functional theory for muon site determination

Studying spin diffusion and quantum entanglement with LF-µSR

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